More broadly, I would not want to be the over-40 guy trying to interview for any team where hardly anyone is even close to 30.
Such teams are quite common, especially in startups everywhere, and not just in SV, unfortunately.
I'm not affected by ageism myself (yet), but even if it was only in SV, which is the biggest tech hub in the US, then it would be a huge problem.
But ageism is rampant outside of SV as well.